California state Sen. Leland Yee leaves federal court in San Francisco on Thursday, July 31, 2014. Yee, who pleaded not guilty, faces charges including racketeering, bribery, and gun trafficking in an organized crime and public corruption case centered in San Francisco's Chinatown.

Photo: Noah Berger / Noah Berger / Associated Press 2014

California state Sen. Leland Yee leaves federal court in San...

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Former San Francisco School Board president Keith Jackson arrives at the Phillip Burton Federal Building and United States Courthouse for his arraignment on Tuesday, April 8, 2014, in San Francisco.

Jackson's attorney, James Brosnahan, said he wants to know the scope of
the agent's financial improprieties, because the agent's undercover work
led federal prosecutors to wiretap the communications of Yee
and Jackson.

(08-15) 09:28 PDT SAN FRANCISCO -- A lead FBI undercover agent was removed from the corruption probe of state Sen. Leland Yee and reprimanded because of his own financial misconduct, according to a new filing by defense attorneys who are seeking to attack the way the case was handled.

According to the government, an agent known in court records as "UCE 4773" - short for undercover employee - had paid former San Francisco school board president and Yee fund-raiser Keith Jackson thousands of dollars.

Jackson's attorney, James Brosnahan, said in court papers filed Thursday that he wants to know the scope of the agent's financial improprieties, because the agent's undercover work led federal prosecutors to wiretap the communications of Yee and Jackson.

The attorney asked for documents detailing the internal FBI investigation into the agent, access to the agent's personnel file and the name of the agent and any others who had contact with Jackson to determine whether other agents engaged in misconduct.

Federal prosecutors have not responded to those requests.

UCE 4773, who posed as an Atlanta businessman during the investigation, engaged in a "pattern of outrageous behavior" before he was "permanently removed" from the investigation, Brosnahan said.

According to the defense filing, the agent "ingratiated himself" by paying Jackson $37,000 in consulting fees in 2012 and 2013, arranged more than $20,000 in donations to a local elected official, considered hosting a $250,000 fundraiser for a "senior elected federal official" and arranged a meeting with a "prominent former athlete" to discuss investing in a hotel project.

Sources have told The Chronicle that undercover FBI agents contributed $20,000 to San Francisco Mayor Ed Lee and also made overtures to former 49ers player Joe Montana, now a developer. Neither the mayor nor Montana have been accused of any crimes.

Brosnahan did not detail the agent's alleged financial improprieties. But he said any wrongdoing by the agent could undermine the case against his client.

He added that several undercover agents in the case, including UCE 4773, had "engineered and directed alleged criminal activity," including initiating discussions of gun sales, offering to facilitate a drug deal and soliciting Jackson to help in an alleged murder-for-hire of a "fictitious victim."

Yee and Jackson have pleaded not guilty to racketeering and other charges contained in an indictment handed down against them, alleged Chinatown gang leader Raymond "Shrimp Boy" Chow and more than two dozen others.